By the time Mrs.Jackson arrived in Shanghai,Mrs.Jackson _______ many famous cities in China.A.visited B.was visiting C.had visited D.has visited
问题描述：
By the time Mrs.Jackson arrived in Shanghai,Mrs.Jackson _______ many famous cities in China.
A.visited B.was visiting C.had visited D.has visited
答
C
答
C by +过去的时间,主句谓语动词用过去完成时态.